A bifunctional VS2–Ti3C2 heterostructure electrocatalyst for boosting polysulfide redox in high performance lithium–sulfur batteries

Abstract

The commercial development of lithium–sulfur batteries (LSBs) is extremely hindered due to the shortcomings of sluggish reaction kinetics and the lithium polysulfide (LiPS) shuttling effect. For overcoming these limitations, a bifunctional VS₂–Ti₃C₂ heterostructure electrocatalyst is designed as a sulfur host material in LSBs, combining suitable adsorption capacity, enhanced catalytic activity, and layer-by-layer interstitial channels to achieve a balanced and efficient “capture-diffusion-catalysis” process. Density functional theory (DFT) calculations indicate that the intrinsically conductive VS₂–Ti₃C₂ possesses an elevated d-band center, improving interaction with LiPSs and accelerating interfacial electron transfer. In addition, the layer interstitial spaces of the 3D lamellar interspersed network facilitate lithium ion diffusion. As a result, LSBs assembled with VS₂–Ti₃C₂/S exhibit a high reversible discharge capacity (1237 mA h g⁻¹ at 0.2C), excellent rate performance (559 mA h g⁻¹ at 10C), and robust cycle stability (0.024% decay rate after 500 cycles at 1C). Moreover, even at a high sulfur loading of 4.0 mg cm⁻², a favorable capacity of 852 mA h g⁻¹ with a capacity retention of 90.5% is still maintained after 150 cycles. This work provides inspiring insights into heterostructure materials with a high rate and sulfur loading in mediating conversions and migrations of matter toward LSBs with promising performance.